Martindale ET4000 / ET4500 Appendix B - Measurement categories
83
Appendix B – Measurement categories
Measurement categories are determined by the potential for dangerous transient
impulses on the mains supply system, the magnitude of which depends on the
amount of damping of the transient energy due to the location within the system and
the system voltage. Short-circuit current levels are also a factor.
Test equipment used for measuring mains circuits will be marked with one or more of
three measurement categories, CAT II, CAT III or CAT IV, to identify on which
installations of a mains supply system it can safely be used.
Each category has a voltage rating marked to indicate the maximum safe phase to
earth system voltage (conventionally 50V, 100V, 150V, 300V, 600V or 1000V).
Transient impulses are greatest for CAT IV 1000V installations.
‘CAT IV 300V, CAT III 600V’ is an example of measurement category marking.
To Next Page
